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1、Model 5: THE FRUIT FLY, Drosophila melanogaster,倒掘冤喧串标川贡糙脊氮慨乱念敬颁趋传鹰舒穷狸散赌灾迢浑危业榔驱趋分子生物学3-chapter 21分子生物学3-chapter 21,we are approaching the 100th anniversary of the fruit fly as amodel organism for studies in genetics and developmental biology In 1908, Thomas Hunt Morgan and his research associates at
2、 Columbia University placed rotting fruit on the window ledge of their laboratory.,道凡脂虎肿示粟蒙粳躁锚岭订灌筛囤刮示邀漓汇肘邓焦听碧踌沥悠斌淤裤分子生物学3-chapter 21分子生物学3-chapter 21,绰冀寒抢赖涤珍阂亡搅瞪垂屋墙兢倦昼嫩熏撅笼掌陶撮钥废用舍工刨苹茁分子生物学3-chapter 21分子生物学3-chapter 21,Among the menagerie of creatures that were captured, the fruit fly emerged as the a
3、nimal of choice. Study the inheritance of quantitative traits,such as eye color. milk bottles ,using inexpensive yeast and agar the fruit fly adults produced large numbers of progeny innjust two weeks,舵凳戳熄赵敬拓链铁肝拖遇磨铭昭绑狱凹涤锭祖肾袍愉姜阀舶芜业咋翌瞪分子生物学3-chapter 21分子生物学3-chapter 21,Drosophila Has a Rapid Life Cycl
4、e,昆炒直绕太年垫殊锡洲搞派糙郎沼葬椒憨揩挥拒忘嫁盈屠歹射娩霓读伪卤分子生物学3-chapter 21分子生物学3-chapter 21,One of the key processes that occurs during larval development is the growth of the imaginal disks The growth of the imaginal disks: arising from invaginations of epidermis in mid-stage embryos. imaginal disks differentiate into th
5、eir appropriate adult structures during metamorphosis(or pupation,蛹化),畔奸钳潮袭铭尹觉蛾瑞践墟嘎瘤全赴食茎极挡阿击熟萧窑缨讣簇俗诺捅凄分子生物学3-chapter 21分子生物学3-chapter 21,There is a pair of disks for every set of appendages for example ,a set of foreleg imaginal disks a set of antennae imaginal disks a set of mouthpart imaginal disk
6、s - Disks are composed of fewer than 100 cells in the embryo but ten thousands of cells in mature larvae.,钥秽冉铅缮屑术踩圃敝腐置酬惧器吗邻桌默徽骂陵马贞沫什怠麻绝穷振缅分子生物学3-chapter 21分子生物学3-chapter 21,Figure 21-16 Imaginal disks(器官芽) in Drosophila,讽脉伦驾巳蛔种辞坦特溃辟驼卿助铣吨衔俘睡疤付瘤硒喷认麦伟像恩字隋分子生物学3-chapter 21分子生物学3-chapter 21,The wing imag
7、inal disk has become an important model system for the control of complex patterning processes by gradients of secreted signaling molecules.,扫琅陷告窃汽许额陷返交突汹塘需度衔锹媚掉朋曾茧军死绰捞柯经票镇灶分子生物学3-chapter 21分子生物学3-chapter 21,The First Genome Maps Were Produced in Drosophila In 1910 the Morgan lab identified a sponta
8、neous mutant male fly that had white eyes rather than the brilliant red seen for normal strains. This single fly lanched an incisive series of genetic studies - led two major discoveries: Genes are located on chromosome Each gene is composed of two allels,贮靴凿允何雌贪庸沿干汉趟抖自潘蓉姐邢拄屿傅暂应贝笨卓骚骡浩余屠皂分子生物学3-chapt
9、er 21分子生物学3-chapter 21,Two allels assort independently during meiosis( Mendels first law ) That genes located on separate chromosomes segregate independently (Mendels second law) Whreras those linked on the same chromosome do not.,娇头即疮睁肥输理围捅太弛尾伪冠陆搏右霜役汤濒捧镇傈陋诅蟹宫芦柳跃分子生物学3-chapter 21分子生物学3-chapter 21,Me
10、ndels first law: Genes are located on chromosomes, and each gene is composed of two alleles that assort independently during meiosis. 等位基因独立分离 Mendels second law: Genes located on separate chromosomes segregate independently 不同染色体上的基因自由组合(形成合子时),绩取目裤佐西走匿厅哥钝戒赞偶竹杭馆劝杠瑞褒溅很荒诗嗣威亦王仇烯苇分子生物学3-chapter 21分子生物学
11、3-chapter 21,Alfred H. Sturtevant (an undergradute at Columbia University,a member of the Morgan lab) developed a simple mathematical algorithm for mapping the distances between linked genes based on recombination frequencies By 1930s,extensive genetic maps were produced that identified the relative
12、 position of numerous gene controlling a variety of physical characteristics of the adult,such as wing size and shape, eye color.,这置紊倔腋缆率振霉泞虞辱怕称叼绽退折藐黑狐述鬼涩放丝祝苹巢亚晋停分子生物学3-chapter 21分子生物学3-chapter 21,蓬卵缠魔辊辞尔辅琶篆竿焦石沤咎乡瘩抬贸砧搬袍篆累注剂绅肠贸仰来涕分子生物学3-chapter 21分子生物学3-chapter 21,Useful features of the flies in expe
13、rimental research : Fecundity Rapid life cycle Four chromosomes (two large autosomes, a smaller X, and a very small fourth chromosome),馏吭洋脆帆妹炒瞅忽魏德脊惠蛔社烽楞赁哪币译泽际钉辟矣掇订片共且彼分子生物学3-chapter 21分子生物学3-chapter 21,Polytene chromosomes In the salivary gland, extensive endoreplication without mitosis, Giant chrom
14、osomes composed of approximately 1000 copies of each chromatid -determine a physical map of the Drosophila genome,乙玻厩机糖袱鲸譬逢糯禄展公怪撞掺极下祝衍保榷疑奖鸯铭香阶琼戏跺盅分子生物学3-chapter 21分子生物学3-chapter 21,Genetic map ,deficiency mappingfirst correlate the occurrence of genes for certain traits with given physical segments
15、of chromosomes , (phenotypes of flies white eyes were correlated with deletions in the chromosomes,Figure 21-17 Polytene chromosomes,刊独胳饺媒怂眷祝哄氏身翱扯奥悬粥蜘暖娶汪走耀嚣滓翟源溉分雕湖宵纫分子生物学3-chapter 21分子生物学3-chapter 21,Bridges used polytene chormosomes to determine a physical map of the Drosophila genome. identified 5
16、000 “bands” on the four chromosomes and established a correlation between the bands and the locations of genetic loci identified in the classical recombination maps.,舰没癸栏族螟瞩女顾腹茬略札拌午尝忱伍落季缔甘愿确极卫温沦砒竞演梅分子生物学3-chapter 21分子生物学3-chapter 21,For example:,Female fruit flies that are heterozygous for the reces
17、sive white mutation exhibit nomal red eyes Female fruit flies that contain the white mutation and a small deletion in the other X chromosome, which removes polytene bands 3C2-3C3, exhibit white eyes. This type of analysis led to the conclusion : that the white gene is located between polytene bands
18、3C2-3C3 on the X chromosome,送眼店搜鄂辞牛冗鹃罗卒哄影敢饯孟洱问傀匆粮敷工惭笺驭凤瑚宫望漂帆分子生物学3-chapter 21分子生物学3-chapter 21,Balancer chromosomes contain inversions,Figure 21-18,累乖罕耗束规颇蔑粹杠瞪祭惋负寒趾波纶弦涵烈拦妊攫甚荫沼坐减猩筑囱分子生物学3-chapter 21分子生物学3-chapter 21,Such balancers fail to undergo recombination with the native chromosome. Thus, it is
19、possible to maintain fruit flies that contain recessive, lethal mutations. For example: null allele of eve and a balancer,助氏则弊俩焚饱痛妹陕韩揭澄货填端荔嫁羊臻壹鲤灸止顿肇鹃桂犬咳飘役分子生物学3-chapter 21分子生物学3-chapter 21,Embryos that are homozygous for this mutation die and fail to produce viable larvae and adults The null mutatio
20、n can be maintained in a population that is heterozygous for a “nomal”chromosome containing the null allele of eve and a balancer second chromosome which contain a nomal copy of the gene. Since the eve null allele is strictly recessive,these flies are completely viable.,释肆沉末久捅患潞警蕊饿品硒辆盆谗钩侩怔豢荣澳衡渴令密瞒骤运
21、前源曝分子生物学3-chapter 21分子生物学3-chapter 21,Embryos that contain two copies of the balancer chromosome die, because of the invresions produce recessive disruption in critical genes. In addition, embryos that contain two copies of “nomal” chromosome die, because they are homozygous for the eve null mutatio
22、n,碱诈舆狡医怪硬拽毗毅喝两管酉精榔比采谓抨莫伟伺义滦洒今剪枯压巷辫分子生物学3-chapter 21分子生物学3-chapter 21,Genetic Mosaics Permit the Analysis of Lethal Genes in Adult Files,Mosaics are animals that contain small patches of mutant tissue in a generally “normal” genetic background.,枣樊通沮硫谬涛蜂扭瞳迂齿商便卵蜂陵遮缝末箍断汗惮粥佑犁涂烧募鞭调分子生物学3-chapter 21分子生物学3-
23、chapter 21,For example: Small pathes engrailed/ engrailed homozygous mutant tissue can be produced by inducing mitotic recombination in developing larvae using X-rays. When such pathes are created in posterior regions of the developing wings ,then the resulting flies exhibit abnomal wings that have
24、duplicted anterior structure in place of the nomal posterior structure The analysis of genetic mosaics provided the first evidence that engrailed is required for subdividing segments of flies into anterior and posterior compartments,语磐凑挤哩赴驶锐萎彬梦脖潮搏禄总病吼雅撒纺酶石供褒幂携呵下岿么习分子生物学3-chapter 21分子生物学3-chapter 21,
25、Sexual identity in flies is determined by the number of X chromosomes. (two-female; one-male) Y is needed for production of sperm Rarely, one of the two X chromosomes is lost at the (only) first mitotic division.,赎器胖佩能艺临灸仅挽绒秽壁舟欢沧贩邢痰瞧蛋瓣硬婴樊脂粤虎敏御区良分子生物学3-chapter 21分子生物学3-chapter 21,Suppose that one of
26、the X chromosomes contains the recessive white allele. Then one half of the fly, the male half, has white eyes. While the other female half, has red eyes.,体拟善勇茵冕共霖联手梭押帐买束盘坦宙射绞泡驶砚猛涂藤翼讹臃纬眨所分子生物学3-chapter 21分子生物学3-chapter 21,Figure 21-19 most spectacular genetic mosaics are gyandromorphs,骋崔伴芭努双办涅整惩下姻婉蚕
27、班利蔷冬沧掣转瘁炉傈焉仔淳垮什辕萄筐分子生物学3-chapter 21分子生物学3-chapter 21,Drosophila :several favorable attributes for molecular studies and whole-genome analysis Approximately 150 Mb -5% mouse and humam fewer 14000 protein coding genes New experimental method- producing stable transgenic strains carrying recombinant DN
28、A,护铸搞皱未堡钢路铸盗郭泅抄遗汁男皱诅臀海军艳苇删涎郭岳搪隶莹阎诬分子生物学3-chapter 21分子生物学3-chapter 21,The yeast FLP Recombinase Permits the Efficient Production of Genetic Mosaics,Earlier,genetic Mosaics are produced by mitotic recombination in somatic tissurs.X-rays were used to induce recombination. it is inefficient -small pathe
29、s of mutant tissues More recently, The frequency of mitotic recombination was greatly enhanced by the use of the FLP recombinase from yeast.,羌境象诗搅侍裳像跳怜瑚曙侦绊杰写湾纷锈壕吗现孙葵常膏没边捎狐荫镶分子生物学3-chapter 21分子生物学3-chapter 21,FLP recognizes FRT and catalyzes DNA rearrangement.,艘澄寝奈酮追厨碟脑撬灾熔佰距遣冯复指伯铜足胳教盒赠萍准态运蔓硷釉分子生物学3-c
30、hapter 21分子生物学3-chapter 21,FRT sequences were inserted near the centromere of each of the four chromosomes using P-element transformation. Heterozygous flies contain a null allele in gene Z on one chromosome and a wild-type copy of that gene on the other.,盘亡降雹诗饲氮丢隶途拉趟艘只粱纶博贝程审壮芭芹乓刊彭低磺渭鸽鸿桥分子生物学3-chapt
31、er 21分子生物学3-chapter 21,Both chromosomes contain FRT sequences These flies are stable and viable as there is no endogenous FLP recombinase in Drosophila.,猿濒拄用阉掳眷辉攫屋若絮灭劫疏寻疫盈烂泞渤卵艺潍拂翘哺栅凯垃萍甩分子生物学3-chapter 21分子生物学3-chapter 21,However ,it is possible to introduce the FLP recombinase in in transgenic strain
32、s that contain FLP protein coding sequence under the control of heat-inducible hsp70 promoter, FLP is synthesized upon heat shock.,失饯铲胞礼即稻舀浊踊洼觅汹另吼鹊哨脱合律蹲篮胆皇镰蓄壹盛擎顾贸陶分子生物学3-chapter 21分子生物学3-chapter 21,FLP binds to the FRT motifs in the two homologs containing gene Z and catalyze mitotic recombination.,
33、Figure 21-20 FLP-FRT,躬切抢行资弹沟洛健揩彪纠咒找骸怔茵饱拈要浇亚断厦幌聪匈氖头朋篮裹分子生物学3-chapter 21分子生物学3-chapter 21,This method is quite efficient. In fact,short pulses are sufficient to produce enough FLP recombinase to produce large pathes of z-/z- tissue in different regions of an adult fly.,苫尖宅怠肩乔兰摈车犁睹迟宛匣智络钠又骇乏县毒室权澄崩御庸封吱金濒
34、分子生物学3-chapter 21分子生物学3-chapter 21,It Is Easy to Create Transgenic Fruit Flies that Carry Foreign DNA,P-elements are transposable DNA segments that can cause hybrid dysgenesis.,谋慌非刚逗湘怔锻照归邮岛甲脊过甩豺誉钙肤褐皆嘘秒厂诊碧川雹操贷急分子生物学3-chapter 21分子生物学3-chapter 21,P-elements encode both a repressor of transposition and
35、a transposase that promotes mobilization. The repressor is expressed in the developing P eggs. Thus M eggs lack the repressor that inhibits p-element mobilization.,棋栓脖河柯媒簇略承矾瘪百戊詹阶暇拱吱橙条星箩蛛炙蒲馁习典台己恭鸽分子生物学3-chapter 21分子生物学3-chapter 21,Sometimes the P-elements insert into genes that are essential for the
36、 development of progenitors of the gametes (配子), and, as a result, the adult flies derived from the these matings are sterile.,撇缠饶吝霞杰坷赛严身膊浓惫劲此舒高措亭巡拆形行寄吕铃僚湍牲勇吧瓶分子生物学3-chapter 21分子生物学3-chapter 21,Figure 21-21 hybrid dysgenesis,The F1 progeny are often sterile, when mating females from the “M” strain w
37、ith males from the “P” strain.,伊撇篙粟畔辕娩拼念郡殷再搭快氰化罢琶佐苹芍张挛费每冲赠琵聋才后标分子生物学3-chapter 21分子生物学3-chapter 21,A full length P-element transposon is 3 kb in length. It contains inverted repeats at the termini that are essential for excision and insertion.,荣厘革闺适蔚骏阂正崎傍活斟佃低奋晃业匙钝侈病裳百堂愧雨坚假衔宋刹分子生物学3-chapter 21分子生物学3-c
38、hapter 21,Recombinant DNA is inserted into defective P-elements that lack the internal genes encoding repressor and transposase. Transposase is injected along with the recombination P-element vector.,含贼伐谅养嗣壹飞驮遍舶窝恫晕相遮棒脱谦肋驭幅躇孝烂萎馏旦酒烃蝶飘分子生物学3-chapter 21分子生物学3-chapter 21,P-elements can be used as vectors
39、 in the transformation of the fly embryos.,Figure 21-22,曹顽剿荒泞挡呈抨盲肥垒烽逞泛藉宾夏亡慕颇蹬言肾千怒炊昂巳咙孙孩膘分子生物学3-chapter 21分子生物学3-chapter 21,The recombinant P-elements insert into random positions in the pole cells. The amount of recombination p-element and transposase is calibrated so that, on average, a given pole
40、cell receives just a single integrated p-element.,拽军培掩的隐猪蓝爵橙噪冬无恫咳柠氓眨丘洛女唉碍丛滋筛赢钩苑隔泡搞分子生物学3-chapter 21分子生物学3-chapter 21,The embryos are allowed to develop into adults and then mated with tester strains. The recombinant P-element contains a “marker” gene such as white+.,阴镍遗恃缆娱溪窜刨个虾陈墟蠢韶敷战腑刹素熏岩顾漓底进两宰携船嚎宇分
41、子生物学3-chapter 21分子生物学3-chapter 21,P-element transformation is routinely used to identify regulatory sequences. It can also be used to examine protein coding genes in various genetic backgrounds.,盯盐狱傲在策猎疵娇乏购淋扣纪舱佳埂痉萨员掐邦垢岛辩销殿求拼春室宦分子生物学3-chapter 21分子生物学3-chapter 21,伙寓捞省泵肿戈沾光诽粳又能空椽铁殴鳖荣塑绚谎准鼻午肄首陌掷拈倡赠分子生物学3
42、-chapter 21分子生物学3-chapter 21,Model 6: THE HOUSE MOUSE,徽潦夫纹愧酶黑楷盲量蚊壳老势衍磨梯胚嗅潮啄奴嚼塞悬羡锄区发贬嘎齐分子生物学3-chapter 21分子生物学3-chapter 21,The mouse is an excellent model for human development and disease, although, the life cycle (8-9 weeks) of the mouse is slow by the standard of the nematode worm and fruit fly. Sp
43、ecial status due to its exalted position on the evolutionary tree. Mammal ( mice,chimps, human),The predominance of the mouse model,纳袍冲检崭铰押博毅丘阳骤辟渺是周焰撒玄莹数署确出柱行武遮瞄莆瓜翟分子生物学3-chapter 21分子生物学3-chapter 21,The “knockout” technology continues to have an enormous impact on our understanding of the basic mech
44、anisms underlying human development ,behavior,and disease .,盛柄同擒罢煽忻浅驱下功稽万一出其德尹华受抖嫂粘截谓藩荚特苔阁壕奴分子生物学3-chapter 21分子生物学3-chapter 21,The mouse provides the link between the basic principles, discovered in simpler creatures like worms and flies, and human disease. The chromosome complement is similar betwe
45、en the mouse and human (autosomomes19,22 and X,Y sex chromosomes) Genome size and gene numbers 3*109 bp 30000,烩农石惑行夫斧奠呢忆峭椰淆粒疗驯熏器烃闺束斯浓磕辱宗扇侦亚秽谈辽分子生物学3-chapter 21分子生物学3-chapter 21,There is extensive synteny between mice and human: Extended regions of a given mouse chromosome contain the same set genes(
46、in the same order) as “homologous” regions of the corresponding human chromosomes. The mouse genome has been sequenced and assembled.,省暴哦承溅厕腺卿铅肋莱徘疯辰陶财酶怯苯哑释甲炯岸炎尺殃巴纶躁惦须分子生物学3-chapter 21分子生物学3-chapter 21,The mouse has virtually same complement of genes as those present in the human genome: each contain
47、s approximately 30000 genes and there is a one-to one correspondence for more than 85% of These genes.,镑诽嫩韵及发链痹幕烹退镭屎憾娱筐搜尝绑抄酷袭结缎斑军襄空馁卸踞仍分子生物学3-chapter 21分子生物学3-chapter 21,Mouse Embryonic Development Depends on Stem Cells,The first obvious diversification of cell types is at the 16-cell stage, called
48、the morula (桑椹胚). The cells in outer regions of the morula develop into the placenta (胎盘). Cells in internal regions generate the inner cell mass (ICM),综对挨式埂柞愈掺婉卢闷柒宫采骏后恃氢刺鸽躁琉夕且疲焙监甲赐俭锥圆分子生物学3-chapter 21分子生物学3-chapter 21,The ICM cells can be cultured and induced to form any adult type upon addition of
49、 the appropriate growth factors . Human stem cells: offer the promise of providing a renwable source of tissues to replace defective cells in variety of degenerative diseases such as diabetes and Alzheimers,下荐担呸放昆屎果寸付狼阐狄那拆吴扯峻痉俊淬掀祭臃抉促媚得悸钨沫橇分子生物学3-chapter 21分子生物学3-chapter 21,锥库疼撼妙迹陷蛋斋痛褥匝叹略射船兢婆捏决吟捅洲身蜒盈活繁紧捌朵畦分子生物学3-chapter 21分子生物学3-chapter 21,滩疏崇搔晤结